The present invention relates to a device for driving washing machine motor using an inverter circuit.
It has been proposed to improve performance of a washing machine motor through vector control using an inverter circuit (an example of such a proposal is included in JP 11090088).
FIG. 28 is a block diagram showing the structure of a washing machine of the above-described category. In FIG. 28, a three-phase induction motor 100 drives an agitator 102, or a spin tub 104. Current detectors 126a, 126b, 126c detect the motor current and control the torque current component and the magnetizing current component independently as vectors for driving the motor via an inverter circuit 124. In this way, the motor 100 is increased in torque at low speed revolution, and driven with approximately the same torque characteristic as a DC brushless motor.
It is also proposed to apply electric braking to a washing machine motor using an inverter, for the purpose of improving the braking reliability and lowering the braking noise caused by a mechanical band brake (an example: the Japanese Laid-open Patent No. 2001-46777). Namely, it aims to improve the reliability by controlling at the revolution retardation of the sinusoidal wave voltage phase by means of PWM control so that the power generation energy is consumed by the internal resistance of a motor, in other words dynamic braking, without causing regenerative energy in a DC source of an inverter circuit.
In the above-described conventional configuration, however, vector technology using an inverter circuit for improving the performance of a motor works to improve torque of a three-phase induction motor at low speed revolution, but it is difficult to improve the efficiency of a motor. Moreover, the low efficiency of the three phase induction motor allows a large current to flow, resulting in increased motor noise. These are problems that need to be solved.
With respect to the electric braking of a motor by means of an inverter control, it needs a complicated control to have the entire power generation energy consumed by the internal resistance of a motor. Furthermore, it does not provide sufficient braking torque for the increasing brake current of a motor.
The present invention addresses the above drawbacks, and aims to offer a compact and energy-conscious motor with which a constant torque control can be performed by changing the motor torquexe2x80x94revolution speed characteristic, and the torque at high speed revolution can be increased, or the efficiency at low speed revolution can be improved.
A washing machine motor drive device in accordance with the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of the motor, a current detector for detecting motor current, and a control device for controlling the inverter circuit. The control device resolves motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with motor control stages. In the above-described structure, motor current of a DC brushless motor is detected to be resolved into a current component corresponding to magnetic flux and a current component corresponding to torque for practicing vector control. At low speed revolution, mainly the current component corresponding to torque is controlled for yielding maximized efficiency, while at high speed revolution, the current component corresponding to magnetic flux is increased in a negative direction for increasing the current through a flux-weakening control for implementing a maximum torque control. Thereby, the motor torquexe2x80x94revolution speed characteristic can be changed and a constant torque control can be implemented. This enables an increase in torque at high speed revolution, or an improvement in efficiency at low speed revolution. Therefore, a motor can be made smaller in size and more energy-conscious.
A washing machine motor drive device in accordance with the present invention comprises a control device, with which device the current component corresponding to magnetic flux and the current component corresponding to torque are controlled independently in accordance with a revolution speed of a motor. In the above configuration, the motor torquexe2x80x94revolution speed characteristic can be modified.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed. This makes it possible to increase the torque at high speed revolution and perform a precise flux-weakening control.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is controlled to be substantially zero when a motor is revolving at a low speed. This makes it possible to revolve a motor at a highest efficiency in low speed revolution.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed for driving a washing/spinning tub for the purpose of dehydration (drying). This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control, and control the dehydration operation covering up to a high revolution speed. As a result, a rate of the dehydration can be increased by increasing the revolution speed.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is increased in the negative direction when a motor is revolving at a high speed for driving an agitator for the purpose of washing. This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control, and control the agitating operation covering up to a high revolution speed. As a result, the washing capability can be increased by strengthening the water flow.
A washing machine motor drive device in the present invention comprises a clothes amount detector for detecting an amount of clothes in a washing/spinning tub, and a control device for controlling the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the amount of the clothes in the washing/spinning tub detected by the clothes amount detector. This makes it possible to increase the torque at a high speed revolution by means of a flux-weakening control in accordance with the amount of clothes, and control the operation covering up to a high revolution speed even in a case where there are many clothes in a washing tub. Thus, the washing capability can be improved, and rate of the dehydration can be raised as well.
A washing machine motor drive device in the present invention comprises a start control device in which the control device controls motor revolution at the startup stage. The start control device performs a direct control on a voltage to be applied to a motor at the startup stage, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently. This makes it easy to introduce a soft-start, where a startup current is suppressed and a starting torque is lowered, and then proceeds smoothly to a current feedback control to the effect of preventing an abnormal increase of revolving speed.
A washing machine motor drive device in the present invention comprises a start control device for controlling motor revolution at the startup stage for the control device. The start control device performs a direct control on a voltage to be applied to a motor at the startup stage, and then controls the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with the revolution speed. Besides making the shift to current feedback control smooth and suppressing the abnormal increase of revolution speed, this makes it possible to use an AC transformer, which is inexpensive, in the current detector. As a result, it is advantageous to implement a motor drive device that is inexpensive yet has high performance.
A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor which is driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, and a control device for controlling an inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently for retarding revolution of a motor. In the above-described structure where a motor current is resolved into the current component corresponding to magnetic flux and the current component corresponding to torque for performing a braking operation through vector control, a highest braking torque is yielded by vector controlling the current component corresponding to torque, while prevention of an abnormal rise of DC voltage in inverter circuit is performed by means of a control on regenerative energy, which is realized through a control on the current component corresponding to magnetic flux.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to torque is controlled to be exhibiting a certain specific value at braking operation. This makes it possible to control a braking torque to be at a certain specific value, and optimize the braking time.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to torque is controlled at braking to show a certain specific negative value. By specifying a negative torque current component, the braking torque can be controlled to show a certain specific value, and the braking time can be shortened.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux and the current component corresponding to torque are controlled at braking to exhibit, respectively, certain specific values. Under this structure, a back electromotive force of a motor and an energy consumption by the internal resistance of the motor can be controlled independently. As a result, the regenerative energy can be controlled, and an abnormal rise of DC voltage in the inverter circuit can be prevented.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux is specified to be greater than that corresponding to torque, at the start of motor braking. This makes it possible to avoid an excessive braking torque exerted at the start of braking, as well as an abnormal rise of DC voltage in the inverter circuit caused by regenerative energy.
A washing machine motor drive device in the present invention comprises a revolution speed detector for detecting revolution speed based on output signal generated from the rotor position detector, and a control device for controlling in accordance with revolution speed, the current component corresponding to magnetic flux and the current component corresponding to torque to exhibit respectively certain specific values at braking. Since a braking torque and an energy consumption by the internal resistance of the motor can be controlled independently in accordance with revolution speed, an increase of regenerative energy in the high speed revolution region, as well as a decrease of braking torque in the low speed revolution region, can be prevented.
A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, a DC voltage detector for detecting DC voltage of the inverter circuit, and a control device for controlling the inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls the current component corresponding to magnetic flux and the current component corresponding to torque independently so that the DC voltage is brought to a certain specific value at braking of a motor. In the above-described structure, where the DC voltage of inverter circuit can be controlled to meet a certain specific value through controlling the regenerative energy, energy for driving the inverter circuit is supplied from the back electromotive force of the motor. As a result, a braking failure at power failure can be prevented.
A washing machine motor drive device in the present invention comprises a control device, with which device the current component corresponding to magnetic flux or the voltage component is controlled at braking so that the DC voltage of an inverter circuit is brought to a certain specific value. Under the above-described structure, since the regenerative energy can be controlled to secure a certain specific braking torque, braking time is kept short even with a power failure.
A washing machine motor drive device in the present invention comprises an alternating current source, a rectifier circuit connected to the alternating current source, an inverter circuit for converting DC power of the rectifier circuit into AC power, a motor driven by the inverter circuit for driving an agitator or a washing/spinning tub, a rotor position detector for detecting the rotor position of a motor, a current detector for detecting motor current, a motor electric power detector for detecting motor electric power, and a control device for controlling the inverter circuit. The control device resolves a motor current into a current component that corresponds to magnetic flux and a current component that corresponds to torque, and controls at braking the current component corresponding to magnetic flux and the current component corresponding to torque independently in accordance with motor electric power. In the above-described structure, the balance between the back electromotive force of a motor and the energy consumption by a motor coil can be judged based on the motor electric power. Therefore, by controlling the current component corresponding to magnetic flux or the voltage component corresponding to magnetic flux in accordance with the small/large of motor electric power, a back electromotive force can be controlled so that it does not cause regeneration in the inverter circuit. Thus, an abnormal rise of DC voltage in the inverter circuit is avoided.
A washing machine motor drive device in the present invention comprises a motor electric power detector for detecting motor electric power, with which a calculation is performed based on the electric power component corresponding to magnetic flux and the electric power component corresponding to torque. Under this structure, since the motor electric power is detected instantaneously, an abnormality in the balance between the back electromotive force of the motor and the energy consumption by the motor coil can be judged instantaneously. Thus, an influence of regenerative power to the DC source in the inverter circuit can be avoided in advance.